Nuclear Weapons Material

This must be deliberate misinformation. It is relatively easy to make two explosive lenses that are exactly alike. It is extremely difficult to make two explosive lenses that differ by a precisely known and constant amount.

No one said it was easy.

The security in a nuclear weapon could certainly be defeated by physically ripping out any encryption electronics and replacing them with electronics with known and simple behavior.

That was the entire point. Having explosive lenses that aren't all the same defeats attacks on the electronics.